A research on the design of smart pressure transmitter

Based on the traditional design, this paper, directed by MODBUS protocol, adds two-wire system and intelligence to the pressure transmitter which boasts a 16-bit embedded microprocessor MSP430F149 that is low in consumption. This transmitter measures the pressure of liquid, gas or vapor with its sensitive piezoresistive components that give small signals of the electric tension and after being magnified, these signals will be output into two wires, one of which firstly goes to the 12-bit A/D located in the microprocessor for data transmission and then through RS485, the measuring results are conveyed to the long-range controlling room; the other of which goes through the module of V/I which transmits the measuring data into current signals of 4~20mA in display. This circuit, after being tested, has promoted the accuracy of the pressure transmitter from the conventional 5% up to 2.5%, which tells the feasibility of the whole design.